Structural and magnetization density studies ofLa2NiO4

Thermodynamic analysis of the ternary La–Ni–O system

“…HTT, LTO, and LTLO stand for the high-temperature tetragonal, low-temperature orthorhombic and low-temperature less orthorhombic phase, respectively. The difference between two lattice parameters of the LTLO phase is very small, so that it can also be considered as tetragonal within the limits of experimental errors: the refinement of diffraction patterns gave the same results for the space groups Pccn and P4 2 /ncm [18,19,30]. [22].…”

“…Earlier studies indicated T N around 650 K [30,42,43], but later [25] this was shown to be caused by the presence of metallic Ni, which has a Curie point at 633 K. The value of the magnetic moment per Ni-atom is assessed as 1.58 ± 0.1µ B based on neutron diffraction measurements [18,25,30]. Both the La 3 Ni 2 O 7 and La 4 Ni 3 O 10 phases crystallize in the orthorhombic cell (Table 1).…”

Neutron scattering studies on stripe phases in non-cuprate materials

“…The structural distortion is suppressed by the Sr doping [51,53] as it is expected by the bond-length mismatch model due to the large ionic radius of Sr and due to the oxidation of Ni similar to the case of La 2−x Sr x CuO 4 [54,55]. La 2 NiO 4 exhibits nn antiferromagnetic order below T N ∼650 K with an ordered moment of 1.6 µB [52] in reasonable agreement with the expectation for S = 1 Ni 2+ with 3d 8 configuration. First evidence for an incommensurate magnetic correlation was obtained in an elastic neutron-scattering study on La 1.8 Sr 0.2 NiO 4 and antiphase domain walls were discussed as one possible explanation [56].…”

“…At 70 K a second structural phase transition occurs into a low-temperature tetragonal (LTT) phase [52]. The LTO and LTT phases are both characterized by tilting of the NiO 6 octahedra but the tilt axes differ: In the LTO phase the tilt axis is along the diagonals of the small perovskite (or parallel to NiO 6 octahedron edge), whereas octahedra tilt around an axis parallel to the bond in the LTT phase.…”

Growth of La2NiO4 thin films by chemical vapor deposition

“…Concerning the films, it is known from the literature that the crystallographic symmetry of La 2 NiO 4+d strongly depends on the value of d [8,9]: it is generally described in a tetragonal or an orthorhombic space group. Concerning the three kinds of films we have studied, the few diffraction lines which appear on the patterns index well using a tetragonal primitive unit cell with a ¼ b ¼ 5.45 Å and c ¼ 12.69 Å .…”